Today, the largest environmental groups in the US joined to send a letter to President Obama voicing their unified opposition to the Keystone pipeline and asking him to block it.

Why is this important?

"For those of us out there in front of the White House, the best thing about this ringing statement is that the administration won't be able to play one group off against another by making small concessions here and there," says protest organizer Bill McKibben.

"There's only one way to demonstrate to the environmental base the rhetoric of Obama's 2008 campaign is still meaningful - and that's to veto this pipeline. Since he can do it without even consulting Congress, this is one case where we'll be able to see exactly how willing he is to match the rhetoric of his 2008 campaign... This is his test."

One couple from Maryland who got arrested says this is a about the clashing between two visions: whether to embrace clean energy, which could one day power millions of electric cars at a price three times cheaper than gasoline - forever - or whether to embrace a massive, 1,700-mile pipeline full of the dirtiest petroleum, steering our nation toward another generation of polluting automobile use.

"A "no" from Mr. Obama would have lasting positive effects. It would send unambiguous signals to Detroit and to Americans everywhere that we've finally turned a corner on our dirty-energy addiction. And, frankly, it would go a long way in shoring up Mr. Obama's badly demoralized base of progressive voters. The president, once again, can be a hero. He can create change we can believe in," says Mike Tidwell and Cindy Parker.

The letter from the Environmental Groups says:

Dear President Obama,

Many of the organizations we head do not engage in civil disobedience; some do. Regardless, speaking as individuals, we want to let you know that there is not an inch of daylight between our policy position on the Keystone Pipeline and those of the very civil protesters being arrested daily outside the White House.

This is a terrible project - many of the country's leading climate scientists have explained why in their letter last month to you. It risks many of our national treasures to leaks and spills. And it reduces incentives to make the transition to job-creating clean fuels.

You have a clear shot to deny the permit, without any interference from Congress. It's perhaps the biggest climate test you face between now and the election.

If you block it, you will trigger a surge of enthusiasm from the green base that supported you so strongly in the last election. We expect nothing less.

TransCanada executives are confident they'll get the permit. Republican politicians and the petroleum industry are crowing about jobs that will be created.

Two major unions disagree. The Amalgamated Transit Union and the Transport Workers Union, which represent over 300,000 workers, sent a joint press release to the State Department, urging it to deny the permit.

"We need jobs, but not ones based on increasing our reliance on Tar Sands oil. ... Many jobs could also be created in energy conservation, upgrading the grid, maintaining and expanding public transportation - jobs that can help us reduce air pollution, greenhouse gas emissions and improve energy efficiency," says the press release.

New York Times Also Opposes Pipeline

In an August 21 editorial, the NY Times took a opposition against the pipeline, citing two main concerns: the risk of oil spills along the pipeline, which would traverse highly sensitive terrain, and the fact that the extraction of petroleum from tar sands creates far more greenhouse emissions than conventional production does.

Building the pipeline would clear the way for Canada to double tar sands production over the next decade to more than 1.8 million barrels a day. To do that, some 740,000 acres of boreal forest - a natural carbon reservoir - would be destroyed.

In addition to the emissions produced by tar sands extraction, would be emissions from the loss of this vast, crucial carbon sink, [editor's note: not to mention the biodiversity it harbors.]